Start with heaviest weight you can that only allows you to do 3-6 reps. Do those reps. Drop down in weight (anywhere from 5 to 20lbs depending). Hit at least 1 more rep than you did the first set. Continue until failure or you run out of weights.

DROP REPS (DESCENDING LADDER)

Pick a weight around 70-80% of your max. Do as many reps as possible. When you come back do 1-2 less reps than last set. Continue for certain number of sets or failure.